Compositions and process of using in refrigeration

ABSTRACT

A blend of refrigerant with at least one fluorosiloxane, which has an SUS viscosity at 100° F. of at least 50 and a pour point of less than about -20° C., is disclosed for use in compression refrigeration.

FIELD OF INVENTION

This invention relates to lubricants used with refrigerants incompression refrigeration and air-conditioning systems. Moreparticularly, it relates to lubricants for use with saturatedhydrocarbons having 1-4 carbon atoms that are partially or fullysubstituted with at least one atom of chlorine or fluorine, and have anormal boiling point of -80° C. to +50° C. Specifically, this inventionrelates to lubricants for use with tetrafluoroethanes, e.g.1,1,1,2-tetrafluoroethane (HFC-134a), and 1,1,2,2-tetrafluoroethane(HFC-134), etc. and of lesser importance, pentafluoroethane (HFC-125).These compounds are being considered as replacements fordichlorodifluoromethane (CFC-12), particularly in automotive airconditioning systems. The lubricants of this invention are not onlycompletely miscible over the full operating temperature range forautomotive air-conditioning with HFC-134a and the like, but are alsocompletely miscible with CFC-12 over this range. Hence, they may be usedwith CFC-12 in the same systems during the transition from CFC-12 toHFC-134a.

BACKGROUND OF INVENTION

Refrigeration systems that use CFC-12 as the refrigerant generally usemineral oils to lubricate the compressor. (See for example thediscussion in Chapter 32 of the 1980 ASHRAE Systems Handbook.) CFC-12 iscompletely miscible with such oils throughout the entire range ofrefrigeration system temperatures, i.e. -45° C. to 65° C. In automotiveair-conditioning, paraffinic and naphthenic oils of about 500 SUSviscosity at 100° F. are usually used with CFC-12. These oils have "pourpoints" below -20° C. and viscosities of about 55 SUS at 210° F. and arecompletely miscible with the CFC-12 refrigerant over the range oftemperatures from -10° C. to 100° C. Consequently, oil which dissolvesin the refrigerant travels through the refrigeration loop in the airconditioning system and returns with the refrigerant to the compressor.It does not separate during condensation, although it may accumulatebecause of the low temperature when the refrigerant is evaporated. Atthe same time, this oil which lubricates the compressor will containsome refrigerant which, in turn, may affect its lubricating properties.

When substituting HFC-134a, HFC-134, or mixtures thereof for CFC-12 inthese refrigeration systems, it would be desirable to be able to use thesame oils as used with CFC-12. It would not require any substantialchange in equipment nor any significant changes in conditions used forthe system. If lubricant separates from refrigerant during operation ofthe system, serious problems may result, i.e. the compressor could beinadequately lubricated. This would be most serious in automotiveair-conditioning systems because the compressors are not separatelylubricated and a mixture of refrigerant and lubricant circulatethroughout the entire system. Unfortunately, however, the mineral oilsare substantially immiscible with the tetrafluoroethanes.

Two recent publications of ASHRAE discuss the problems associated withseparation of lubricants and refrigerants. These are "Fundamentals ofLubrication in Refrigerating Systems and Heat Pumps" Kruse and SchroederASHRAE Transactions Vol. 90 Part 2B, pps. 763-782, 1984 and "Evaluationof Lubricants for Refrigeration and Air-Conditioning Compressors",Spauschus, ibid pps. 784-798.

In summary, refrigerants which are not completely miscible with an oilin the full range of mixture compositions and operating temperatures maybecome miscible or immiscible as the temperature is raised or loweredfrom room temperature. The areas of immiscibility may assume a varietyof shapes, i.e. parabolic or non-parabolic. As a parabola, the curve ofmiscibility temperature vs. percent oil in the mixture, may have itsopen or concave portion facing the low or high temperatures. The closedor convex-portion of the parabolic curve identifies, respectively, themaximum or minimum temperature above or below which the refrigerant andthe lubricating oil are completely miscible. These temperatures arereferred to as the maximum or minimum "consolute temperatures." Besideparabolas, these curves can assume skewed parabolic shapes or curves ofvarying slope wherein immiscibility occurs above or below the curve.

One of the objects of this invention is to provide a combination oflubricating oil and refrigerant such as tetrafluoroethane, e.g.HFC-134a, where the area of miscibility encompasses the full range oftemperature and composition encountered in compression refrigeration,i.e. complete miscibility occurs for all compositions in the range of-45° C. to at least 20° C., preferably to 100° C., the criticaltemperature of HFC-134a. Another object is to provide a process forusing such compositions in compression refrigeration.

PRIOR ART

U.S. Pat. No. 4,248,726, issued Feb. 5, 1981, and U.S. Pat. No.4,267,064, issued May 12, 1981, both to Nippon Oil Company et al, relateto the use of a polyglycol oil such as polyoxypropylene glycol (or analkyl ether thereof) having a viscosity index of at least 150 and aglycidyl ether type epoxy compound as a high viscosity refrigeration oilcomposition for halogen-containing refrigerants. Thesepolyglycol/glycidyl ether compositions are disclosed for use with Freon®11, 12, 13, 22, 113, 114, 500 and 502; and as being "particularlyeffective" with Freon® 12 or 22.

Research Disclosure 17486 entitled "Refrigeration Oil by E. I. du Pontde Nemours and Company discloses polyalkylene glycols such as Ucon®LB-165 and Ucon® LB-525 sold by Union Carbide Corporation, for use withHFC-134a. These glycols are polyoxypropylene glycols that aremono-functional and are prepared from propylene oxide initiated withn-butanol. The publication states that these combinations of oil andrefrigerant are miscible in all proportions at temperatures at least aslow as -50° C. and are thermally stable in the presence of steel, copperand aluminum at 175° C. for about six days.

U.S. Pat. No. 4,755,316, issued Jul. 5, 1988, to Allied-Signal Inc. alsorelates to the use of polyalkylene glycols. However, these glycols areat least difunctional with respect to hydroxyl groups and contain atleast 80% propylene oxide units relative to the total, the remaining 20%may derive from ethylene or butylene oxide or esters, olefins and thelike which are polymerizable with propylene oxide.

Japanese 118598 Kokai Patent No. HEI 1(1989)-118598, published May 11,1989, by Idemitsu Kosan Company, discloses the use of a polysiloxanehaving the following formula as a lubricant with a variety ofrefrigerants including hydrogen-containing Freon® chlorofluoroalkanesand perfluoroalkanes: ##STR1## in which R³ and R⁴ are selected amongalkyl groups containing 1-20 carbon atoms, aryl groups containing 6-30carbon atoms, cycloalkyl groups containing 6-30 carbon atoms,fluorine-substituted alkyl groups containing 1-20 carbon atoms,fluorine-substituted aryl groups containing 6-30 carbon atoms, andfluorine-substituted cycloalkyl groups containing 6-30 carbon atoms; R⁵through R⁸ are selected among fluorine-substituted alkyl groupscontaining 1-20 carbon atoms, fluorine-substituted aryl groupscontaining 6-30 carbon atoms, and fluorine-substituted cycloalkyl groupscontaining 6-30 carbon atoms; m is a constant of 1-100".

SUMMARY OF THE INVENTION

The present invention is based on the discovery that the use of asufficient amount to lubricate, usually 10-20% by volume for automotiveuse, and in some situations as high as 50% by volume, of a lubricantcomprising at least one fluorine-containing compound having the formula:##STR2## in which R¹ and R¹⁰ are each selected from the group consistingof alkyl groups containing 1-20 carbon atoms, aryl groups containing6-30 carbon atoms, and cycloalkyl groups containing 6-30 carbon atoms;at least one of R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹ is selected from thegroup consisting of fluorine substituted alkyl groups containing 1-20carbon atoms, fluorine-substituted aryl groups containing 6-30 carbonatoms and fluorine-substituted cycloalkyl groups containing 6-30 carbonatoms; and the remainder of R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹, if anyare not fluorine-substituted, are selected from the group consisting ofalkyl groups containing 1-20 carbon atoms, aryl groups containing 6-30carbon atoms and cycloalkyl groups containing 6-30 carbon atoms; andwherein y is a number from 1-50 and x is a number from 0 to 50, whereinthe sum of x and y is equal to 1-60, preferably 2-30; the lubricanthaving an SUS viscosity at 100° F. of at least 50 and a pour point ofless than about -10° C., with usually 80-90% by volume of at least oneof the tetrafluoroethanes, HFC-134 and HFC-134a, the pentafluoroethane,HFC-125, and any other saturated hydrocarbon having 1-4 carbon atomsthat is partially or fully substituted with at least one atom ofchlorine or fluorine and a normal boiling point of -80° C. to +50° C.,will be completely miscible in one another in the range of temperaturesfrom -40° C. to at least 20° C., preferably to 100° C., the criticaltemperature of HFC-134a.

The preferred fluorosiloxane oils of this invention may be defined as atleast one having the same structural formula as given above but whereonly one of R², R³, R⁴, R⁵, R⁶, R⁷, R⁸ and R⁹, preferably R⁵, isselected from the aforementioned fluorine-substituted alkyl, aryl orcycloalkyl groups; y plus x is anywhere from 1-30, preferably 2-14 ifonly R⁵ is selected from the fluorine-substituted groups and the ratioof x- to -y should be no greater than 3, preferably 0.

The most preferred fluorine-substitution for R⁵ is afluorine-substituted alkyl group having the formula

    --(CH.sub.2).sub.m --(CF.sub.2).sub.n F

where "m" is 2-6, preferably 2, and "n" is 1-10, preferably 4-8.

Specific fluorosiloxane oils which have been found most useful in thisinvention include ##STR3## and mixtures thereof.

Another compound that may be used, although not preferred, is acommercial product described in Kokai Patent No. HEI 1 (1989)-118598having the formula: ##STR4## wherein x is about 12.

It is believed that the lubricants of this invention utilize thelubricating qualities of the siloxanes wherein "x+y" is the viscositycontroller. Thus, an "x+y" of 2 will usually provide an SUS viscosity at100° F. of about 150 wherein an "x+y" of 14, an SUS viscosity at 100° F.of about 3000-5000. It is also believed that "m+n" controls lubricity.The miscibility with refrigerants is believed to be a function of thefluorine-substituted groups attached to the siloxanes and is controlledby the ratio of x- to -y. Surprisingly, some of the less uniformfluorine-substitution of the preferred fluorosiloxane lubricants, usedeither alone or in blends, provides excellent miscibility with HFC-134athroughout the refrigeration cycle of -45° C. to 100° C.

The weight ratio of refrigerant to the lubricant, the fluorine-modifiedsiloxane oil, may be anywhere from 99/1 to 1/99, preferably 99/1 to70/30. The viscosity of these oils may range from 50 to 3000 SUS at 100°F., but for most commercial uses, from 100 to 1200 SUS at 100° F.

It is known that the use of an appropriate amount of an "extremepressure (EP) additive" improves the lubricity and load-bearingcharacteristics of oils and, thus, would improve the quality of therefrigerant-lubricant compositions. EP additives for use in theinvention are included among those disclosed in Table D of U.S. Pat. No.4,755,316. A preferred one is an organic phosphate; SYN-O-AD® 8478, a70%/30% blend of tri (2,4,6-tri-t-butyl phenyl) phosphate/triphenylphosphate, manufactured by AKZO.

EP additives may also be used in conjunction with some of the antiwearadditives, oxidation and thermal stability improvers, corrosioninhibitors, viscosity index improvers, detergents and anti-foamingagents disclosed in Table D of U.S. Pat. No. 4,755,316. These additivesmay also be partially or fully fluorinated.

DESCRIPTION OF PREFERRED EMBODIMENTS

As stated previously, the tetrafluoroethanes, e.g. HFC-134a, HFC-134 andthe pentafluoroethane, HFC-125, particularly HFC-134a have physicalcharacteristics which allow substitution for CFC-12 with only a minimumof equipment changes in compression refrigeration. They could be blendedwith each other, as well as with other refrigerants, including CFC-12(CCl₂ F₂), HCFC-22 (CHClF₂), HFC-152a(CH₃ CHF₂), HCFC-124(CHClFCF₃),HCFC-124a(CHF₂ CClF₂), HCFC-142b(CH₃ CClF₂) , HFC-32(CH₂ F₂),HFC-143a(CH₃ CF₃), HFC-143(CHF₂ CH₂ F), and FC-218 (CF₃ CF₂ CF₃); andfor purposes of the present invention such blends are not excluded.However, only those blends of tetrafluoroethane or pentafluoroethanewith other refrigerants which are miscible with the lubricants of thisinvention in the range of -40° C. to about +20° C. are included.

HFC-134a, the preferred tetrafluoroethane refrigerant, may be preparedby any of the methods disclosed in the prior art; e.g., U.S. Pat. Nos.2,745,886; 2,887,427; 4,129,603; 4,158,675; 4,311,863; 4,792,643 andBritish 1,578,933 and 2,030,981.

The preferred polyfluoroalkyl siloxanes are commonly prepared byhydrosilation of fluorine-substituted alpha-olefins using Pt and Rucatalysts.

However, I have found that the use of cobalt catalysts, namely Co₂(CO)₈, provide excellent yields of the fluorosiloxane. Specifically, thesiloxanes for use in this invention were prepared by reacting for 24-72hours perfluoroalkylethylenes with hydromethylsiloxanes at a temperatureof 20°-50° C. using 0.1-3% by weight of a Co₂ (CO)₈ catalyst. Thus, thesiloxanes listed earlier as (1)-(4) were prepared by hydrosilylation ofperfluoroalkyl olefins (F(CF₂)nCH═CH₂,n=4,6,8) withpolymethylhydrosiloxanes (Me₃ SiO(SiHMeO)_(k) SiMe₃,k=3,5,14) and for(5) and (6) with methylhydro-dimethylsiloxame copolymer, all using theCo₂ (CO)₈ catalyst. For some fluorosiloxanes, particularly partiallyfluorine-substituted siloxanes, it may be more convenient to use H₂PtCl₆ ·6H₂ O or Pt divinyltetramethyldisiloxane complex as the catalyst.

The broad class of fluorosiloxanes useful in this invention can also beprepared using the methods described, in general, in the followingpatents and publications:

U.S. Pat. Nos. 3,642,626 and 4,818,423, German Patent No. 3,710,423,European Patent No. 89104821.7, Kokai Patent No. HE1 (1989) - 118598 andJapanese Patent No. 1-153792.

The fluorosiloxane oils may be varied to yield viscosities ranging from50 to 3000 SUS at 100° F. They may be blended with each other and withother lubricants, e.g. perfluorocarbons, other hydrofluorocarbons,naphthenic, paraffinic, alkylbenzenes, polyalkyl benzenes, etc., tomodify viscosity and/or lubrication properties.

Specifically, the lubricants used in the compositions of the invention,and in the invented method for providing lubrication in compressionrefrigeration and air-conditioning equipment have the followingcharacteristics:

Viscosity at 100° F.

50 to 3000 SUS, preferably 100 to 1200 SUS, particularly about 500 SUSfor automotive air-conditioning

Pour Point

-10° C., preferably below -15° C. for the 100 SUS and 500 SUS oils.

Solubility or miscibility range

100% from 100° C. to less than -40° C. for 1-99 weight percent ofHFC-134a in mixture with the lubricant of 100° F. viscosities of 50 SUSto 2500 SUS.

Four-ball wear test with a specific set of steel balls

Scar wear and coefficient of friction equal to or slightly higher thanthat for the oils currently used with CFC-12 in automotiveair-conditioning, i.e., 0.37 mm scar wear and 0.07 friction coefficientwhen saturated with CFC-12 at atmospheric pressure.

"Falex" (load-to-failure) test with a specific type of steel for theV-block and pin

The fail load equal to or greater than that for the CFC/refrigerant oilcombinations, i.e., 1300 lbs. when saturated with CFC-12 at atmosphericpressure.

1. Solubility of Refrigerant in Lubricants

Six ml. blends of refrigerant and lubricant were used for the solubilitystudies. Generally, the mixtures contained 30, 60 and 90 wt. %refrigerant. These air-free mixtures were contained in sealed Pyrex®tubes (7/16" I.D.×5.5", ca. 12.5 cc capacity). The refrigerant/lubricantsolubilities were determined by completely immersing the tube in a bathat each test temperature for a minimum of 15 minutes and providingagitation to facilitate mixing and equilibration. The accuracy ofdetermining the temperatures when the refrigerant/lubricant blend becameeither miscible or immiscible was about ±2° C. The refrigerant/lubricantblends were called immiscible when the blend acquired and retained"schlieren" lines; formed floc; became cloudy or formed two liquidlayers. These solubility tests were run from 93° to -50° C. Tests werenot run above 93° C. for safety reasons. It is assumed that if the blendof HFC-134a/oil is soluble to 93° C., it will still be soluble at 100°C., the critical temperature of HFC-134a.

2. Stability of Refrigerant and Lubricant

One or three ml of lubricant alone or 1 ml each of refrigerant andlubricant plus coupons (steel 1010/copper/aluminum1100--23/8"×1/4"×1/16", 120-grit surface finish) were charged and sealedin a Pyrex® tube (7/16" I.D.×5.5", ca. 12.5 cc volume) under anaerobicconditions. The specimens were tied together at the top end with copperwire with copper-wire rings between the metals to separate the metals atthe top end. The tubes were stored vertically at 400° F. for 11.8 days.Afterwards, the tube contents were examined for appearance changes.These changes were assigned effect ratings: 0--no change; 1--slightacceptable change; 2--borderline change; 3--slight unacceptable change;and 4--moderate unacceptable change.

The oil in some cases was removed from the tube to determine if thelubricant degraded by measuring its viscosity at 100° F.

3. Lubricity

a. Four-ball Wear Test

The procedure is described fully in ASTM D4172. The method was modifiedas follows: A load of 20 Kg at 1200 RPM was put on the steel 52100 ballsimmersed in 10 ml. of lubricant at 225° F. for 60 minutes. Therefrigerant gas, HFC-134a or CFC-12, was bubbled through a Teflon®capillary tube into the lubricant at the rate of 0.75 standard cu.ft./hr. to provide one atmosphere of pressure of refrigerant gas overthe lubricant and a gas-saturated lubricant.

b. Falex Pin/V-Block Load-to-Failure Test

The procedure is described fully in ASTM D3233. The V-Block was made ofAISI C-1137 steel (HRC-20 to 24 hardness, 5 to 10 microinches surfacefinish). The test pin was made of AISI 3135 steel (HRC-87 to 91hardness, 5 to 10 microinches surface finish). These tests were run withrefrigerant gas bubbling through the oil as in the "Four-ball WearTest".

4. Viscosity and Viscosity Index

a. Viscosity is a property that defines a fluid's resistance to shearingforce. It is expressed in terms of absolute viscosity, kinematicviscosity or Saybolt Seconds Universal viscosity (SSU), depending on themethod by which it is determined. Conversion from SSU to mm² /s(centistokes) can be readily made from tables contained in ASTM D-445,but it is necessary to know the density to convert kinematic viscosityto absolute viscosity. Refrigeration oils are sold in viscosity grades,and ASTM has proposed a system of standardized viscosity grades forindustry-wide usage (D-2422).

Viscosity decreases as the temperature increases; and increases as thetemperature decreases. The relationship between temperature andkinematic viscosity is represented by:

    log log (v+0.7)=A+B log T

where v=kinematic viscosity, mm² /s (CST) T=thermodynamic temperature(kelvin) A,B=constants for each oil

This relationship is the basis for the viscosity temperature chartspublished by ASTM and permits a straight line plot of viscosity over awide temperature range. This plot is applicable over the temperaturerange in which the oils are homogeneous liquids.

b. Viscosity Index is a measure of the amount of change in viscosityexperienced by an oil with change in temperature. It is determined inaccordance with the ASTM method described in D2270-79.

5. Pour Point

Any oil intended for low temperature service should be able to flow atthe lowest temperature likely to be encountered. The procedure fordetermining pour point is described in ASTM D-97-66.

The invention will be more clearly understood by referring to theexamples which follow.

EXAMPLE 1-2

The following fluoroalkylsiloxanes were prepared using the proceduredescribed previously: ##STR5## Specifically, they were prepared by thehydrosilylation of F(CF₂)_(n) CH--CH₂ wherein "n" was 8 and 4,respectively, with Me₃ SiO(SiHMeO)_(k) SiMe₃ wherein "k" was 3 and 14,respectively, using a Co₂ (CO)₈ catalyst. The reactor was loaded witholefin (65 ml) and the silane (20 ml). Then 3 g of the Co₂ CO₈ catalystwas added to the reactor. The temperature was maintained between 20° and50° C. and the system was stirred magnetically for 24 to 72 hours. Theresulting product was washed with methyl alcohol; diluted with CFC-113;filtered through activated carbon and activated alumina; and evaporatedunder vacuum to provide a greater than 75% yield of thefluoroalkylsiloxane lubricant as determined using proton molecularresonance ('H NMR).

The lubricants were analyzed for molecular weight, glass transitiontemperature (by differential scanning calorimetry), viscosity, viscosityindex and pour point; and tested for miscibility with thetetrafluoroethane refrigerant, HFC-134a, over the range of temperaturesfrom -50° C. to 93° C. using 10-70 weight percent fluoroalkylsiloxane inmixture with HFC-134a. The results are given in Table 1.

                  TABLE 1                                                         ______________________________________                                         Example                                                                             Lubricant  Molecular Weight                                                                           % F(a) Tg(b)                                   ______________________________________                                        1      (1)        1700         58     -58° C.                          2      (2)        4400         54     -65° C.                          ______________________________________                                                           Viscosity          Pour                                    Ex-   Miscability  SUS         Viscosity                                                                            Point                                   ample with HFC-134a                                                                              100° F.                                                                        210° F.                                                                      Index  (°C.)                          ______________________________________                                        1     -40° C. to 93° C.                                                             381     56    97    -42                                   2     -40° C. to 93° C.                                                            1734    223   198    -39                                   ______________________________________                                         (a)wt. % fluorine                                                             (b)glasstransition temperature                                           

EXAMPLE 3

The following fluoroalkylsiloxane was prepared substantially asdisclosed in Examples 1-2 but wherein "n" for the fluoroolefin was 6 anda methylhydro-dimethyl siloxane copolymer

    Me.sub.3 SiO(SiHMeO).sub.k (SiMe.sub.2 O).sub.1 SiMeH3

wherein k and 1 were each 6. ##STR6##

Similar properties and miscibility were determined as in Examples 1-2and the results are given in Table 2.

                  TABLE 2                                                         ______________________________________                                         Example                                                                              Lubricant Molecular Weight                                                                            % F  Tg                                       ______________________________________                                        3       (3)       3000          49   -77° C.                           ______________________________________                                                           Viscosity          Pour                                    Ex-   Miscability  SUS         Viscosity                                                                            Point                                   ample with HFC-134a                                                                              100° F.                                                                        210° F.                                                                      Index  (°C.)                          ______________________________________                                        3     -40° C. to 93° C.                                                            443     84    198    -48                                   ______________________________________                                    

EXAMPLE 4-6

The following three fluoroalkylsiloxane oils were prepared and tested asin the previous examples: ##STR7##

                  TABLE 3                                                         ______________________________________                                        Miscability of HFC-134a with Lubricant                                        (Test range 93 to -50° C.)                                             Example Lubricant Wt. % HFC   Miscable Range (° C.)                    ______________________________________                                        4       (4)       30, 60      93 to -50                                                         90          93 to -45                                       5       (5)       30          93 to -40                                                         60          93 to -5                                                          90          87 to 20                                        6       (6)       30          93 to -37                                                         60          93 to -5                                                          90          93 to 20                                        ______________________________________                                    

                  TABLE 4                                                         ______________________________________                                        Stability of HFC-134a/Lubricant Mixture in Contact                            with Steel-1010 (Fe), Copper (Cu), and Aluminum-1100                          (Al) at 400° F. for 11.8 days                                                                       100° F.                                   Lubri-                                                                              Volume Ratio           Viscosity                                                                            Effect Rating                             cant  Lubricant/Refrigerant                                                                        Liquid  (SUS)  Fe  Cu   Al                               ______________________________________                                        (4)   3/0            0       613    .sup. 0.sup.a                                                                     0    .sup. 0.sup.a                          1/1            0       567    .sup. 0.sup.a                                                                     0    .sup. 0.sup.a                    (5)   1/0            0       --     0   0    0                                      1/1            0       --     0   0    0                                (6)   1/0            0       --     0   0    0                                      1/1            0       --     0   0    0                                ______________________________________                                         .sup.a trace tarnish                                                     

                  TABLE 5                                                         ______________________________________                                        Other Properties of Lubricant (4), the                                        Blend, with HFC-134a Compared to                                              CFC-12 with Sunisco ® 5G5*                                                                      Commercial                                                            (4)     Oil                                                     ______________________________________                                        Viscosity (SUS)                                                               100° F.  856       533                                                 210° F.  140       57                                                  Viscosity Index 141       52                                                  Pour Point (°C.)                                                                       -34       -23                                                 4-Ball Wear                                                                   Wear Scar (mm)  0.45.sup.(a)                                                                            0.37                                                Coefficient of Friction                                                                       0.08      0.07                                                Falex Load-to-Failure                                                         Fail load (lbs.)                                                                              2250.sup.(b)                                                                            1250                                                Fail torque (in lbs.)                                                                         48        24                                                  ______________________________________                                         .sup.(a) after test, appeared clear, colorless                                .sup.(b) after test, translucent black color (Incipient seizure at 2250       lbs. but no seizure to maximum load of 4500 lbs.)                             *500 SUS, 38% aromatic naphthenic oil manufactured by Witco Chemical Co. 

What is claimed:
 1. A composition for use in compression refrigerationcomprising: (a) at least one compound selected from the group consistingof 1,1,2,2-tetrafluoroethane, 1,1,1,2-tetrafluoroethane andpentafluoroethane; and(b) a sufficient amount to provide lubrication ofat least one fluorine-containing compound having the formula: ##STR8##in which R¹ and R¹⁰ are each selected from a first group consisting ofalkyl groups containing 1-20 carbon atoms, aryl groups containing 6-30carbon atoms, and cycloalkyl groups containing 6-30 carbon atoms, R⁵ isa fluorine-substituted alkyl group having the formula

    --(CH.sub.2)m--(CF.sub.2).sub.n F

wherein m is an integer from 2 to 6 and n is an integer from 4 to 8; andR²,R³,R⁴, R⁶,R⁷,R⁸ and R⁹ are selected from the group consisting ofaikyl groups containing 1-20 carbon atoms, aryl groups containing 6-30carbon atoms and cycloalkyl groups containing 6-30 carbon atoms; whereiny is a number from 2-14 and x is equal to zero, said lubricant having anSUS viscosity at 100° F. of at least 50 and a pour point of less thanabout -10° C.
 2. The composition of claim 1 wherein component (a) is1,1,1,2-tetrafluoroethane and component (b) is ##STR9##
 3. Thecomposition of claim 1 wherein component (a) is1,1,1,2-tetrafluoroethane and component (b) is ##STR10##
 4. Thecomposition of claim 1 wherein component (a) is1,1,1,2-tetrafluoroethane and component (b) is ##STR11##